Fractionating apparatus



March 11, 1930. E. H. HARRIS FRACTIONATING APPARATUS Filed Aug. 6, 1926lllln lilll /N I EY TOR y izjw' Patented Mar. 11, 1930 UNITED STATESPATENT OFFICE ELIOT HUNTINGTON HARRIS, F PITTSBURGH, PENNSYLVANIA,ASSIGNOR TO BENJA- MIN M. HERB, OF IITTSBURGH, PENNSYLVANIAFRACTIONATING APPARATUS Application filed August 6, 1926. Serial No.127,564.

This invention relates to apparatus for obtaining substantially completefractionation of liquids from mixtures, such as binary, or more complexmixtures, containing such liquids.

Various mixtures of liquids are obtained from natural sources, and it isoften desirable to separate certain of the liquids contained in v themixture for the purpose of obtaining them 0 in a substantially purestate. While this can ordinarily be accomplished in a laboratory,certain difficulties are encountered when the process of fractionationis attempted on a a commercial scale. For example, it is highlydesirable to produce motor. fuels having certain specificcharacteristics from mixtures of hydrocarbon liquids which are availablein natural sources of supply, and while the theories of fractionation orseparation are well understood, it has heretofore been impossible toeconomically carry out such theories on a commercial scale. As'a result,the production of motor. fuel having highly desirable characteristicswhich are obtained by complete fractionation has been so costly as to ineffect make the price of such fuel prohibitive when compared with theprice of less satisfactory but commercial fuel.

An object of my invention is the production of apparatus which isrelatively cheap to build and operate but which may be employed inobtaining substantially complete fractionation of liquids from mixturesavailable in natural sources of supply or such as result frommanufacturing processes.

' In the oil refining industry, it is particularly desirable to separatecertain hydrocarbon liquids from mixturescontaining the same, and one ofthe objects of the present invention is to produce apparatus whichrenders it possible to separate certain hydrocarbon liquids, insubstantially pure state, from liquid mixtures containing the same. Itwill, however, be apparent that the apparatus 43 herein illustrated anddescribed may be used in the fractionation of. liquids other than thoseusually classed as hydrocarbons In the single sheet of drawingsaccompanying and forming a part hereof, I have illustrated what I nowconsider to be the preferred form of apparatus, but it will be apparentto those skilled in the art that various changes and modifications maybe made therein with-' out departing from the spirit and scope of theinvention as hereinafter more particularly set forth. if

The apparatus illustrated includes a still 1, in which a liquid mixture,such as crude oil or naphtha, is vaporized by being subjected to heat.'The still is of the usual form em ployed in distillation processes andis provided with a dome 2 from which the vapors are delivered throughpiping 3'. The delivery end of the piping communicates with afractionator or heat exchanger 4 which is provided at its inlet end witha head 5 having an inlet port 6 and secured to a cylindrical shell 7 Theshell 7 encloses a plurality of tubes or vapor passagesS which are inopen communication at their inlet ends with a chamber formed by the head5 and which terminates at their outlet ends in a similar chamber formedby a head 9 secured to the shell 7 and provided with an outlet port 10.The interior of the shell is shown divided into a number of fluidcirculating chambers 11 by means ofv diaphragms 12. In the drawings, twosuch.

. diaphragms are illustrated and the end tubes 8 extend through and aresecured in tube sheets 12. .This arrangement of tube sheets anddiaphragms provides three liquid circulating chambers 11. Each of theseis provided with a liquid inlet port 13 and a liquid discharge port 14.These ports are so connected to liquid circulating systems as to includeeach chamber 11 in one system.

The fractionator is so formed or located that the tubes 8 are inclinedupwardly from their inlet to their delivery, ends, and the vapor outletport 10 of the head 9 or of the fractionator communicates through a pipe15, with a condenser, of the type usually em-- ployed in commercialdistillation processes.

The theories of fractionation have been well established, as isexemplified by United States Patent No. 1,171,464 to Rosanofi' of Feb.15, 1916,- but it has been impos-. sible to economically carry forwardthese theories on a commercialscale since the cost matter of fact,apparatus heretofore developed has been commercially impractical. One ofthe features of the present invention is that the heat extraction fromthe gaseous vapors traversing the f 'actionator is accomplishedgradually, with the result that the vapors are cooled to a predeterminedtemperature as they traverse the f 'actionator but at the same time thecooling process is gradual and the temperature of the vapors isgradually reduced from the inlet to the outlet end of the fractionatorwithout being subjected to zones of sudden temperature changes. For thisreason, the apparatus may be operated in such a way as to successfullycarry forward the theories of complete fractionation wherein thetemperature of the mixed vapor is gradually reduced and the condensateoccasioned by the reduction in temperature is permitted to flow back toa region of predetermined higher temperature at which it is againvaporized and again carried forward with the vapors moving through thefractionator.

For the purposes of illustration, I have shown three chambers 11 formedwithin the shell 7 and each forming a part of a separate liquidcirculating system. It will be apparent that each such system is adaptedto abstract and carry heat away from the gaseous vapors traversing thetubes 8. It will also be apparent that where a relatively largereduction in temperature is necessary to obtain complete fractionationof a particular liquid, from a mixture containing that liquid, a largenumber of such chambers would have to be employed if the theories,expound.- ed by Rosanoif, are to be satisfied in the fullest. degree andif no other means were employed for the purpose of I obtaining thegradual reduction in the temperature of the vapors. I, however, avoidthe necessity of employing a commercially impractical number of coolingchambers, but at the same time obtain the advantage of the completefractionation theories, by employing means in connection with eachchamber, such that the heat transfer from the vapors,,traversing thetubes 8, is controlled and the vapors gradually cooled, even though thecirculating liquids delivered to successive chambers 11 vary materiallyin. temperature.

This is accomplished in the illustrated embodnnent, by employmg a seriesof baffles 16 in each chamber 11 so arranged as to vary the rate of flowof cooling fluid past different portions of each tube 8 in each chamberand in this way control the rate of heat transfer from the vapors to thefluid so as to minimize or avoid abrupt changes in the temperatures ofthe vapors as they pass from the region of one circulating systemito theregion of another.

Asshown, the inlet port 13 of each chamber 11 communicates with a. pipe17 forming a part of a circulating system through which cooling fluid,such for example as oil having a high flash point, is delivered by apump 18. Each outlet port ll of each chamber 11 communicates with a pipe19 which in turn communicates with the inlet of the pump 18. Inaccordance with the theories of complete fractionation and also inaccordance with the mode of operation to be employed in connection withthe apparatus here disclosed, it is essential that the temperature rangein each of the various chambers 11 be maintained at substantially apredetermined temperature. For this reason, I have disclosed means forcontrolling the temperature of the fluid deliw ered to each of thechambers 11 in order that the desired determined temperature at theinlet may be maintained. As shown, by way ofillustration, I employ a.separate heatcr 20 and cooler 21 in each circulating system, and theheater and cooler are separately controlled by the temperature of thefluid leaving them. As shown diagrammatically, the heater 20 is providedwith gas or oil burners 22 and the supply of fuel to these is controlled by a valve 23 which is diagrammatically shown as controlled by athermostat 24 located in the outlet pipe 25 of the heater. Oil isdelivered to the heating coil 26 of the heater through a pipe 27 whichcommunicates with the delivery port of the pump 18. The pipe 25communicates with the inlet of the cooler 21 which is similar inconstruction to an ordinary surface condenser and is provided with aninlet 28 and an outlet 29 for cooling fluid, such as ammonia gas,pentane or water.

The flow of cooling fluid is controlled by a valve 30 located in thewater inlet piping 28, and this valve is in turn controlled by athermostat 31 which is located in the piping 17. The outlet to thecooler communicates with the pipe 17 and consequently oil traversing thecirculating system is delivered from the cooler direct to the inlet port13 of the associated chamber 11.

, lVith this arrangement, the circulating oil is delivered atsubstantially the predetermined temperature to the associated inlet port13. It will, of course, be apparent that the temperature control isobtained by either the thermostat valve 23 or the valve 30 or by theco-operation of both the heater and the cooler. 'It will be apparentthat the valve 23 maybe so arranged as to completely shut oil theburners (a pilot flame being employed to relight them) and that thevalve 30 may entirely close off the flow of cooling water through thecooler. lVith such an arrangement, either the cooler or the heater willgenerally be in operation as such, but at the same time the method ofcoupling them in the circulating system makes it possible for one toco-operate with the other in producing the desired temperature of thecirculating liquid at the inlet to the associated chamber 11. Theeffectiveness of the cooler is varied in response to the variations inthe temperature of the circulating liquid leaving the cooler, with theresult that the cooler responds quickly to any variation in thetemperature of the oil and maintains the circulating oil delivered tothe fractionator at the desired temperature. V

In order to obtain the desired rate of heat 7 transfer from the vaportraversing the tubes 8 to the circulating fluid of each system or toobtain the desired temperature range in each chamber 11, I control therate of flow of the circulating fluid in each system, in response to thetemperature of the fluid as it leaves the associated chamber 11. This isaccomplished in the apparatus illustrated by vary ing the steam supplyto the engine or turbine driving the pump 18 in accordance with thetemperature of the circulating fluid leaving the port 14 of theassociated chamber 11.

For simplicity of illustration, the driving engine of each pump 18 isnot shown, but a steam supply piping 32 leading to the engine is shownand is provided with a valve 33 which is controlled by means of athermostat 34 located in the pipe 19 immediately adjacent to theassociated port 14. With this arrangement, the rateof circulation of thecooling fluid, and consequently the rate of heat transfer within eachchamber 11, will be controlled by the rise in temperature of thecirculating fluid as it traverses the chamber i 11 forming a part of itscirculating system.

It will be apparent that where a fluid such for example as pentane gasis employed as the cooling medium, the pump will not be employed, butthe control will be accomplished by means of a thermostaticallycontrolled throttle valve.

" tionating temperature but at the same time to avoid subjecting thevapors to temperature shocks or to abrupt changes in temperature.

It will be apparent to those skilled in the art that the temperatures ofthe circulating fluids delivered to the various chambers 11 of thefractionator may be such as to produce a gradual reduction in thetemperature of the vapors traversing the tubes 8 of the fractionator,and that in this way, these vapors may be cooled to any desiredtemperature to accomplish the substantially complete fractionation of aparticular liquid having a delinite boiling point, and that thisfractionation may be accomplished from mixtures, containing the liquidin question, even though those mixtures are binary or more complex miX-tures.

One of the important features of my invention is the method of bafflingemployed in each of the chambers 11 for the purpose of obtaining thepredetermined rate of heat transfer for each unit of length of the tubes8. In determining this baffling, it is essential to determine thedesired temperature for the circulating liquid at the inlet and outletof the chambers 11. The pitch, i. e. the spacing of the baffles 16ineach chamber is then determined in accordance with the rate of heattransfer that it is desired to obtain from one end of the chamber to theother. For example, if the rate of heat transfer is to be graduallyreduced in the direction of the vapor flow in the tubes 8, then in theapparatus illustrated, the baflies would be close together at the vaporinlet end of each chamber 11 and would be spaced further apart as theyapproach the vapor delivery end of that chamber, it being understoodthat in the illustration, the flow of circulating liquid iscountercurrent to that of the vapors traversing the tubes 8. It is,therefore, possible to obtain a proper spacing of the baffles which willprovide an increase or a decrease in the temperature increment per unitof length. ofheat transfer surface of the tubes 8, so as to give thecorrect-and predetermined temperature zones to the vapors passingthrough the tubes 8 for proper fractionation in accordance with thetheories of complete fractionation.

It will, therefore, be apparent that the pitch of the baffles can bedetermined from the liquid and-vapor phase'curves of the particularmixtures to be fractionated and that the temperature of the vaporstraversing the tubes 8 may be predetermined according to the laws offractionation by proportioning the inlet temperature of the circulatingliquid and the rate of flow of that liquid through the chamber and thebaffle pitch. Those skilled in the art will understand that the transferrate of any particular design of apparatus will vary, but may beempirically determined by known methods, and this transfer rate,together with the other data above mentioned, will then be employed inthe determination of the baflie pitch. It'will also be apparent that byadopting the proper temperature gradient for any specific mixture to befractionated, a single chamber may replace the three chambers 11illustrated in the drawings and the varying pitch of the baffles may besuch as to maintain any desired rate of heat transfer per unit of lengthof tubes 8 so as to give the desired predetermined temperature of thevapor at every point along the tubes 8, for a complete fulfillment ofthe laws of fractionation. It will, of course, be apparent that theelimination of the multiplicity t chambers 11 will materially simplifythe apparatus, since it will avoid the necessity of employing more thanone circulating system and a large number of temperature controls.

In operation, the temperature of the vapors traversing the tractionatoris gradually re duced to the predetermined temperature of thecirculating liquid entering the vapor de livery end ofthe tractionator,with the result that condensation is taking place at different pointsalong the tubes 8 and the condensate so formed is draining back intoregions of higher temperature, and is being re-vaporized s described.The condensate which does not vaporize at temperatures encountered inthe fractionator is returned through the reflux tube 35, and the vaporsleaving the traction ator through the port 10 are delivered to acondenser where they are condensed.

In many cases, the temperature of the vapors entering the fractionatorthrough the inlet port 6 varies materially during a run. In order toaccomplish true fractionation, it may therefore be desirable tocontinually vary the temperature of the cooling fluid within the chamber11 to correspond with variations in the temperature of the vaporentering through the port 6.

In order to accomplish this and also avoid the necessity of manualcontrol, I employ a thermostat 44, diagrammatically shown with the bulbor thermo-couple in the vapor pipe 3. This thermostat controls theoperation of the thermostat 31 with the result that a predetermineddilference is maintained between the temperature of the vapors enteringthrough the port 6 and the temperature of the cooling fluid delivered tothe chamber 11. This is accomplished by so arranging the thermostat 44that it varies the position of the control or adjusting device 31 whichforms a part of the thermostat 31 and is diagranr matically shown on thedrawings.

It will be apparent to those skilled in the art that structure such asillustrated is adapted for use as an independent or integral plant, andthat where a continuous supply of circulating fluid is available, as ina refinery employing continuous stills, the use of the separatecirculating system may be avoided by employing oil from the stills asthe cooling medium.

lVith such an arrangement, the same gen eral mode of operation would beemployed and the thermostats would be similarly placed.

It will also be apparent that the temperature of the incoming coolingmedium should be so proportioned with relation to the temperature of theincoming vapors and the known heat transfer rate of the fractionator asto produce temperatures within the vapor passages of the fractionatorthat correspond with the temperatures necessary for true fractionationand that this may readily be accomplished by adjusting the apparatusherein set forth.

While I have illustrated but one embodiment of my invention, it will beapparent to those skilled in the art that changes and modifications,other than those herein described, may be made therein without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

lVhat I claim is 1. Apparatus of the character described, comprising atractionator provided with at least one passage for vapors received froma source of vapor, means for delivering aflow of fluid to saidfractionator and in heat transferring relation with said vapor passage,means for delivering the fluid at substantially a predeterminedtemperature, and means tor varying the rate of flow of said fluid atdiflerent points along said passage to obtain variable rates of heattransfer from the vapors to the fluid at different points along saidpassage, to thereby obtain predetermined changes in the temperatureincrement of the vapors per unit length of the heat transfer surface ofsaid passage.

2. An apparatus of the character described, comprising an unobstructedvapor line receiving vapor at its lower end and delivering vapor atitsupper end, a shell surroundin said line and having liquid inlet andoutlet ports, a closed circuit including said shell, means forcirculating fluid through said circuit in contact with said line, meansresponsive to the temperature of the fluid at the inlet port of saidshell for maintaining the fluid entering the shell at substantially apredetermined temperature, means dependent on the temperature of thefluid after it has received heat from the vapor for controlling saidcirculating means to vary the rate of fluid flow through said shell, andmeans within said shell for varying the rate of flow of the liquid pastsuccessive portions of said line to control the rate of heat interchangealong said line.

3. A'fractionator comprising a vapor passage, a shell surrounding saidpassage and provided with a fluid inlet port and a liquid outlet port,means for circulating a cooling fluid through said shell in contact withsaid passage, means for maintaining a predetermined temperature of thefluid entering said shell through the inlet port thereof, meansdependent on the temperature of the fluid leaving the shell through theoutlet port thereof for controlling said circulating means to vary therate of flow of the fluid traversing the shell and to maintain apredetermined temperature diflerence between the fluid entering and thefluid leaving the shell, and baffles Within the shell for directing theflow of fluid along said passages, and so spaced as to vary the rates ofheat transfer per unit lengths of heat transfer surface of said passagealong the passage and thereby the temperature increment per unit lengthof said passage of the vapor traversing the passage.

4. A fractionator of the tube and shell type having an inlet forcondensable vapors communicating With one passage thereof and an inletfor cooling fluid communicatin With another passage thereof, meansincluding a thermostat subjected to the temperature of the cooling fluidleaving said fractionator for maintaining the fluid entering thefractionator at a predetermined temperature, and a thermostat subjectedto the temperature of the vapor entering the fractionator for varyingthe adjustment of the first mentioned thermostat.

5. Fractionating apparatus, comprising a shell, at least one vaporconveying passage extending therethrough, means for deliver- I ingcondensable vapors to said passage, said passage extending upwardly fromthe vapor inlet to the outlet end thereof, means for delivering fluid tothe interior of said shell in heat transferring relation to saidpassage, means for varying the temperature and means for varying therate of flow of such fluid at diiferent points along said passage tocontrol the rate of heat transfer between the fluid so delivered and thevapors traversing said passage.

In testimony whereof, I have hereunto subscribed my name this 4th day ofAugust,

E. HUNTINGTON HARRIS.

